RealMedia files (.rm and .rmvb) don’t play or play without sound
A: You are missing a decoder for RealAudio COOK. You can install that by following these steps:
Download the Windows version of binary codec pack for MPlayer.
(filename = windows-essential-20071007.zip)
Extract only these files from the ZIP archive:
cook.dll, pncrt.dll, sipr3260.dll, drv33260.dll, drv43260.dll
Put those files in the Windows system folder.
That is C:\Windows\System32\ on a 32-bit version of Windows.
That is C:\Windows\SysWOW64\ on a 64-bit version of Windows.